Cerebral Cortex

Abstract

The cerebral cortex is a telencephalic structure present in some vertebrate species located at the surface of the cerebral
hemispheres. It is the brain area most recently acquired in evolution. The cerebral cortex resembles a six layer sheet of
neurons that in many animals, including humans, is folded to fit into the confines of the skull. Each cerebral cortex hemisphere
is made of four anatomically distinct lobes: frontal, parietal, occipital and temporal. Within these lobes, different cortical
functions are carried out by functionally and anatomically distinct cortical areas. Although structurally similar, the two
hemispheres of the cortex are not functionally equivalent. The cerebral cortex is involved in many higher‐level functions
such as sensory perception, cognition, language, memory, decision making, motor planning and control.

Key Concepts

The cerebral cortex is well‐organised anatomical structure with six neuronal layers and subareas that are anatomically and
functionally distinct.

The cerebral cortex is composed of different neuronal subtypes that are organised into networks that connect neurons within
and between distinct functional areas.

A large part of the cerebral cortex is devoted to processing sensory stimuli from the environment.

The remainder of the cortex is devoted to motor planning and control, as well as integration of multiple sensory cues and
cognitive processing.

The two hemispheres of the brain are similar in organisation but distinct in some functions.

The complex networks of the cerebral cortex are specified in development using intrinsic molecular cues and spontaneous neuronal
activity, although sensory‐driven activity can also play a role.

Figure 3. Circuitry of the cerebral cortex. Neurons in different layers have stereotyped projections including feedforward, feedback
and lateral connections. Neurons with similar properties are arranged in a columnar manner suggesting that single columns
containing canonical circuits may be the basic unit of processing in the cerebral cortex.

Figure 4. The sensory and motor homunculi. A homunculus is a little person represented in the motor (a) and somatosensory (b) cortex
delineating the amount and location of cortical space devoted to sensing or moving the appropriate body part. The representation
is distorted such that areas that require fine motor control or that provide a lot of information about the sensory world
(such as fingers) occupy a relatively larger cortical space. Notice that while the motor and sensory homunculi are similar,
they are not identical (This figure is redrawn from Penfield and Rasmussen, ).